well, I guess its time... another FF with way to much crap on it.

[svstee]

As you may have gathered from the title, I want to build a fuzz face with a lot of knobs and switches. I am aware of just how many times this has been done, but I have some ideas I haven't seen on other stuff.

My main goals here are economy, variety, reliability, and practicality, in that order.

I do not want to use any Ge transistors, this thing is all Si, in keeping with the goals of economy and reliability.
I want to add a three band tonestack.
I want some sort of bias indicator as well as a bias pot. I was thinking about just using a voltometer display (so I can "tune" to 4.5v) built in.
I want to use a DIP switching setup to switch between a bunch of transistors for Q2.
I want an "input volume" control, simply a 100kA pot before the input, doing the same basic thing as the knob on the guitar.
I do not need options for crazy glitch/fart/oscillation type effects.

I had another idea for the bias indicator. Would it be possible to wire up an LED so that it gets brighter as voltage increases but the shuts off when voltage is over 4.5 volts? Maybe something with a Zener diode or an LDR, I can't figure out how to do it though.

So my questions are:
1: Favorite tonestack for the Si FF?
2: Where is the best place to implement said tonestack?
3: How can I set up a decent bias indicator?
4: Would there be any point to having multiple transistor options for Q1?

[kurtlives]

Adding a tonestack seriously takes away from the FF sound. You would also need a recovery stage. Adding switchable input caps would be a better idea imo.

With a DIP switch to switch transistors you'll need to switch in each leg of both transistors I believe. Why not just use a DPDT or 3PDT switch?

With Ge transistors you dont want to bias to 4.5V. Most like somewhere in the 6V - 7V region.

Check out GGG for adding a input gain control, its just like a variable voltage divider.

[svstee]

With a DIP switch to switch transistors you'll need to switch in each leg of both transistors I believe. Why not just use a DPDT or 3PDT switch?

Because I want to be able to choose between upwards of 6 different transistors. Can't I just wire all the base legs together?

With Ge transistors you dont want to bias to 4.5V. Most like somewhere in the 6V - 7V region.

As I said, I'm not using Ge, all the transistors will be Si.

[punkin]

Tonemender?
If you're wanting to go old school add an Analog DC meter on the front or an LED driven circuit to trigger when your 4.5 is achieved (this could get messy)

[svstee]

Ooooh, tonemender....post or pre fuzz?

That's what I meant when i said voltometer display, DC meter. Seemed like overkill to me though. I guess I'll go with it if I can't figure out the LED.

Any ideas for the LED trigger? that would be ideal I think.

[Nasse]

I think it will be big size any way so it is best to build few perfectly tuned ffs inside rather than try to make one do everything, which might lead to sacrificing what ya are looking for- perhaps two is enough with lot of knobs of course some of them can be common

Has anybody tried to mess with the negative feedback, like eq or something...

[svstee]

If I have a pot to control bias I don't see a problem with the number of transistors I have available. The differences between, say, a 2n5889, 2n2222 and a BC109 are substantial.

Anyone have any ideas about that LED trigger?

[GREEN FUZ]

You may have seen this already, but if not, it might give you some ideas.

http://www.buildyourownclone.com/ptpfuzz.pdf

BYOC thread here.

http://www.buildyourownclone.com/board/viewtopic.php?f=23&t=1132&st=0&sk=t&sd=a

[svstee]

I had not seen that actually, thanks!
Gave me a couple ideas to incorporate as well, like the bass cut and voltage sag.

[JKowalski]

For the LED, use a comparator with it's reference voltage set at 4.5V. You could also use another comparator with its voltage trigger set up slightly above 4.5V, and then invert it's output. So you have one that outputs HIGH when you hit 4.5 and LOW when it's below, and another that outputs LOW when you hit, say, 4.55 and outputs HIGH when you are below 4.55V. Then put each comparator output into an "and" gate? Thatll give you a on state when the voltage is between those two comparator ref. voltages.

There's got to be an easier way... But I just thought I would throw that out there.

If you never want it to go below 4.5V, maybe use a zener to regulate the voltage at the transistor terminal? Then you only need that first comparator to check when it gets to 4.5V.

[svstee]

I don't think Ill go the Zener route, I want to be able to set bias wherever I want, but also to be able to quickly set it at 4.5. I think I might have to break down and just a a DC meter display.

[JKowalski]

Well, then use the comparator. Now that I thought of it, you dont need the inverter, just an OR gate. That's only two chips right there - A dual comparator, and a OR gate. Very little space. And you can set the ranges for the LED to trigger pretty exactly. If you want, I can try to draw up a schematic for you.

EDIT: Well, actually, it's way too simple to bother drawing a schematic. Just get a dual comparator, put a 4.45 voltage divider as the (-) input to one and a 4.55V divider as the (-) input to the other one. Put the transistor terminal input to each of the (+) terminals on the comparators. Put a pull up resistor on the outputs of both comparators, and drive a OR logic gate with the outputs (the resistor value depends on the logic type). Take the OR output, and use it to drive your LED! That simple. You could even have ONE voltage divider, at 4.5 Volts, with a diode in the middle, taking the two comparator inputs from either side of the diode (the diode drop will determine the range of the ON state, so you could use a 0.6V normal diode drop range, or maybe a schottky diode with a 0.2V range.)

All told, thats... 7 components total, not counting the LED. That's barely anything.

EDIT II:

Whatever - here you go. I believe this will work well, correct me if I am wrong. The LM7805 is needed for logic gates - unless you can find a good XOR gate that can run on 9V?



I just reread your first post and noticed that you were looking for something that gets brighter, then shuts off. In any case, I think comparators are the way to go. Just use the comparator to trigger at slightly above 4.5V and use the HIGH output to disconnect the LED current path, which will be fed by the transistor voltage, (buffered?)